Terraria, the absolutely superb Minecraft-meets-side-scrolling-platformer, is to get a retail release. For, er, £20. The digital version costs £6 at most, regularly dropping to amazing bargain prices during various sales, and is unquestionably amazing value. But £20 for an “Exclusive Collectors Edition” when it’s a year old, in a box, in a shop? That seems a little strange.